The present invention relates to a printer apparatus.
With the development of electrical image equipment, image recording has been frequently carried out using an ink jet printer head or a thermoelectric printer head. In particular, the development of large-sized heads and multiheads is advancing for the purpose of high-speed printing.
However, in the case of printing, for example, in ink jet image printing, the amounts and the jet directions of inks jetted from respective nozzles of a printer head are scattered, and thus the scattering results in printing unevenness, such as a line to the eye. This printing unevenness becomes more conspicuous in larger-sized heads and multiheads. Thus, line-like unevenness arises periodically on a printed image at an interval of the width of the printer head. This results in a remarkable deterioration in image quality. There also arises a problem that in printing over a long period this unevenness changes with the passage of time.
U.S. Pat. No. 5,285,220 discloses a method for correcting such density unevenness.
Specifically, as shown in FIG. 17, a print image data is binarized in a binarization processing section 2, and for printing with a printer head 3, an unevenness correcting table 1 is arranged at the previous stage of the binarization processing section 2. Using this unevenness correcting table 1, the print image data is corrected. Correction of scattering in respective nozzles of the printing head makes it possible to correct density unevenness. Furthermore, considering the fact that density unevenness is different in accordance with the tone of image data to be printed even if the same nozzle is used, the correction corresponding to the tone of the image data is also carried out.
In the aforementioned U.S. Pat. No. 5,285,220, at the time of correcting each nozzle of the head, a density unevenness detecting chart is used to measure the tone characteristic of each of the nozzles, and a tone (gray level)-correcting characteristic for correcting this characteristic is memorized for each of the nozzles. In the case of, e.g., 8 bit data, however, the graduation has 256 tones and a considerably large memory capacity is necessary in order to memorize correction data for every tone for all of the nozzles. Moreover, much time is spent for detecting density unevenness using the density unevenness detecting chart of the 256 tones.
Therefore, an object of the present invention is to provide a printer apparatus that makes it possible to decrease a memory capacity for memorizing correction data necessary for correcting density unevenness and that cuts the down time for detecting the density unevenness.